Voters in California, New Jersey, New Mexico, North Dakota, South Dakota and Montana took to the polls on Tuesday to cast their preference between Sanders, a U.S. senator from Vermont, and former Secretary of State Clinton. And while the Democrats continued to battle it out at the polls, Trump notched a series of uncontested wins and delivered a wide-spanning address from Briarcliff Manor, New York.

Trump attacked Clinton, promised a better future for the country, and — perhaps most importantly — made a pitch for the highly-energized Sanders supporters.

"To all of those Bernie Sanders voters who have been left out in the cold by a rigged system of superdelegates, we welcome you with open arms," Trump said. "And by the way, the terrible trade deals that Bernie is so vehemently against — and he's right on that — will be taken care of far better than anyone ever thought possible."

Donald Trump and Hillary Clinton, presidential candidates

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Again playing on some Sanders supporters' complaints about Clinton winning through an unfair system (irrespective of the fact that she entered Tuesday night topping Sanders in the popular vote and pledged election-based delegates — in addition to superdelegates), Trump positioned himself as the candidate to break such a structure.

"This election isn't about Republican or Democrat, it's about who runs this country: special interests or the people," he said. "Why would politicians want to change a system that's totally rigged to keep them in power? That's what they're doing folks. Why would politicians want to change a system that's made them and their friends very very wealthy?"

"I beat a rigged system by winning with overwhelming support — the only way you could've done it," Trump added. "We can't fix a rigged system by relying ... on the very people who rigged it."

As for the general election against Clinton, Trump struck a confident note against a political family he alleged had "turned the politics of personal enrichment into an art form."

"Recent polls have shown that I'm beating Hillary Clinton, and with all of her many problems, and the tremendous mistakes that she's made — and she's made tremendous mistakes — we expect our lead to continue to grow, and grow substantially," Trump said.

As for specific complaints against Clinton, Trump said he is preparing a "major speech on probably Monday of next week" that will discuss "all of the things that have taken place with the Clintons."

"I think you're going to find it very informative and very very interesting," Trump said as applause erupted.

Sanders' camp contested Clinton's "presumptive" designation given by NBC, the Associated Press and others, arguing that superdelegates are free to change their preference until the party's convention in July. As the campaign and its supporters correctly identified, neither Clinton nor Sanders are likely to win the required 2,383 delegates without incorporating supers into their count, but that remains a daunting task.

By NBC's count, Clinton had won 1812 pledged delegates and held the support of 573 superdelegates (making 2,385) before Tuesday's polls closed. Sanders, on the other hand, only had a total of 1,567 combined delegates, according to NBC.

And that margin is not just a quirk of a convoluted primary system, as Clinton has easily bested Sanders in the season's total popular vote going into Tuesday — by more than 3 million, according to most counts.

Still, Sanders has vowed to fight on to the convention, arguing that he is the best candidate to take on Trump in the general election.

"Our job from now until the convention is to convince those superdelegates that Bernie is by far the strongest candidate against Donald Trump," Michael Briggs, Sanders' spokesman, said in a Monday statement.